Each weekend during the summer, upwards of 10,000 people stream onto the small peninsula in the Potomac known as Hains Point, transforming it into Washington's largest block party. They come to exercise, meet new friends, or simply sit in the cool breeze that blows off the water.

And many, odd as it may seem, go there to get into a traffic jam, their freshly waxed cars inching along Ohio Drive so that drivers and passengers can see and be seen.

"I come down here to look at all the pretty young ladies," Arlington resident Charles Dangerfield, 19, a student at Virginia State University, said Saturday, as people geared up for another weekend on the Point. "And they're all here looking for fellas, just like we're looking for them."

Others enjoy the 21 tennis courts, Olympic-size swimming pool, 36 holes of golf, and acres of plush green grass that make the 327-acre park one of Washington's most popular playgrounds.

"This is one of the most beautiful places in the world, and the weather is gorgeous," said Fran Sullivan, winner of the Miss Aqua Follies Beauty Pageant that was held at Hains Point back in 1948. Now in her late 50s, she and her husband, a Navy aviator, lounged yesterday under one of the many cherry trees that line the Hains Point shoreline, and watched planes take off and land at National Airport, across the Potomac.

Their day was made all the more pleasant by unseasonably mild August weather, a peak of 85 degrees and 40 percent humidity yesterday afternoon. After five days of milder weather, brought about by cool, northwesterly winds from Canada, temperatures were expected to return today and through the week to the 90s, with increased humidity.

Whatever the weather, Washingtonians seem to find Hains Point an oasis.

On Saturday traffic streamed into East Potomac Park at the rate of 800 cars, 84 vans, 12 mopeds, and 84 bicycles per hour. "And that's a slow day," according to U.S. Park Police officer Mike Owens.

Yesterday, a busier time, even more cars crawled around the 2.3 miles of Ohio Drive, slowing traffic to a top speed of 3 miles per hour.

Many automobile enthusiasts, like Dangerfield, drove to Hains Point at the start of the weekend to wax and polish their cars.

Stereos cranked up full blast, shirts off, beers close at hand, they filled the side of the road with their own automobile show. Blue Jaguars, yellow Corvettes, green BMWs, red Datsuns lined the road in an explosion of style and color.

Dangerfield, the proud owner of a beige Chevette, was somewhere down in the pecking order, but that didn't bother him. "I pick up two or three phone numbers everytime I'm here," he said.

A number of people whistled and applauded as a fleet of ten Pontiac Firebird Trans-Ams revved their engines and pulled to a stop along the shoulder of the road. They call themselves Thunder-Am, Inc., and each weekend they meet at Sam's Car Wash in Marlow Heights to make the journey, en masse, to Hains Point, according to club members. They arrive early in the day to make sure they can find the 30 or 40 yards of roadside necessary to park together.

"It's the psychology of the whole thing," explained a club member, John Armstrong, 24. He said that the sight of 10 Trans-Ams -- "sleek, compact and fast" -- is very impressive. "We just hang out, and when girls come by, we give then a little wink, show them the car, and ask if they'd like to go for a ride."

While cars and meeting new people are for many the premier attractions at Hains Point, other people come simply to relax and watch the world go by.

Eloise Harris, 60, known affectionately to her Northeast Washington neighbors as "Grandma," has "fond, sentimental memories" of her first romantic rendezvous at Hains Point in the early 1940s. She now visits the park to sit on its benches, watch the children play and relax in the cool breeze.

Out on the tip of the peninsula, where the waters of the Washington Channel meet the Potomac River, the atmosphere was filled with the sounds and smells of a carnival. Smoke from charcoal grills thickened the air with tantalizing aromas of sweet and tangy barbecue sauces, while enormous stereos rocked with sound. Young people clapped their hands, sang songs and danced together on top of picnic tables.

Bruce McGee, 32, first came to Hains Point with his parents when he was too young to remember. Now, he and his wife, Yvonne, continue the family tradition with their three children. "I come here for the pretty view, to spend time with my family, to get away from things," he said Saturday. "It's like being in your own world."

"This is a great beat . . . ," said officer J.F. Robinson, who on weekends patrols the park from horseback. "People are here for relaxation. There's very little crime -- no domestic problems. Everyone's very congenial."

The park itself is man-made, built atop tons of silt reclaimed from the bottoms of the Potomac River and the Washington Channel. Construction began in 1882, when Congress appropriated funds for Lt. Col. Peter C. Hains of the Army Corp of Engineers to dredge the waterways so commercial traffic could pass more freely.

Despite the lovely scenery and friendly people, not everyone enjoys cruising around in circles for 45 minutes at 3 miles per hour, and for a motorist caught unaware, it can be a nightmare.

"What's going on up there?" one such agitated driver said on Saturday, stepping from his car to survey the stalled line of traffic after he had not moved an inch in five minutes.

"It's okay, man," replied an amused bystander, pointing to the cause of the congestion: a car full of men stopped in the middle of the road to chat with a group of women. "They're just having a little conversation!"